A physical model for the spectral-timing properties of accreting black holes
A physical model for the spectral-timing properties of accreting black holes
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DOI：
10.1093/mnras/sty2133
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发表时间：
2018-03
影响因子：
4.8
通讯作者：
Ra’ad D Mahmoud;C. Done
中科院分区：
文献类型：
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作者：
Ra’ad D Mahmoud;C. Done
我们开发新的技术去卷积的X射线发射区域的径向结构在明亮的低/硬态的黑洞天鹅座X-1使用光谱和定时数据在3-35千电子伏的范围。在这些能量下的光谱是由康普顿化而不是圆盘所主导的，但是在不同能带之间的时间滞后以及这些能带的功率谱的归一化和形状的差异中存在复杂的模式，这清楚地表明康普顿化不是从单个均匀区域产生的。我们使用一个物理为基础的模型，通过一个频谱不均匀的流传播的密度波动，通过联合拟合的时间平均和傅立叶分辨光谱设置的光谱分量。任何波段的预测变化都是在傅立叶空间中解析建模的，因此它可以直接拟合到观测到的功率谱和滞后。我们发现，最佳拟合模型挑选出三个不同的半径的流动，每个具有不同的康普顿谱。在这些半径处产生的变化和光度被增强，而来自较大半径的波动的传播被抑制。我们将这些半径与圆盘截断、流动的内边缘和（更推测性地）喷气发动半径相关联。这些不同的半径在源接近低/硬和高/软状态之间的过渡的情况下是最明显的。我们认为，在较低的光度下看到的平滑的功率谱意味着源结构是简单的过渡。
We develop new techniques to deconvolve the radial structure of the X-ray emission region in the bright low/hard state of the black hole Cygnus X-1 using both spectral and timing data in the 3–35 keV range. The spectrum at these energies is dominated by Comptonization rather than the disc, but there is a complex pattern in the time lags between different energy bands and differences in the normalization and shape in the power spectra of these bands, which clearly shows that the Comptonization is not produced from a single, homogeneous region. We use a physically based model of density fluctuations propagating through a spectrally inhomogeneous flow, setting the spectral components by jointly fitting to the time-averaged and Fourier-resolved spectra. The predicted variability in any band is modelled analytically in Fourier space so it can be fit directly to the observed power spectra and lags. We find that the best-fitting model picks out three distinct radii in the flow, each with a distinct Compton spectrum. The variability and luminosity produced at these radii is enhanced, while propagation of fluctuations from larger radii is suppressed. We associate these radii with the disc truncation, the inner edge of the flow, and (more speculatively) the jet launch radius. These distinct radii are most evident where the source is close to a transition between the low/hard and high/soft states. We suggest that the smoother power spectra seen at lower luminosities imply that the source structure is simpler away from the transition.